Optical Properties and Aging of Gasochromic WO$_{3}$

WO$_{3}$ as a possible optical gas sensor has gained increasing importance with H$_{2}$ becoming a major fuel of the future. This has led to efforts to understand the theoretical and practical aspects of the gasochromic behavior of WO$_{3}$. WO$_{3}$ films were fabricated using pulsed laser deposition (PLD). Morphological and stoichiometric ratios of films obtained were observed as functions of deposition parameters. We present the optical constants induced by 2{\%} H$_{2}$:Ar in WO$_{3}$ films. This allows us to obtain the limits of the gasochromic change in comparison to ion injection. It was found using Langmuir's adsorption equation that at low H$_{2}$ concentrations a high sensitivity is predicted but the coloration could saturate at 57.9 {\%} of the material's maximum ion adsorption. Poisoning of the films was also addressed by coating with a permeable polydimethylsiloxane layer. It is shown that gasochromic degradation is prevented thus eliminating common atmospheric gases as possible contaminants. Our studies suggest WO$_{3}$ thin films as highly sensitive and stable optical hydrogen sensors.